1. Field of the Invention
The present invention relates to a layered coil component. In particular, the present invention relates to a layered coil component including a coil formed by layering electrically conductive members and insulating layers and a method for manufacturing the layered coil component.
2. Description of the Related Art
For example, a layered coil component to be used for a DC-DC converter is required to have good DC bias characteristics in order to prevent reduction in the conversion efficiency of current to magnetic energy due to reduction in inductance resulting from magnetic saturation.
An open magnetic circuit type layered coil component described in Japanese Examined Patent Application Publication No. 1-35483 has been known as a layered coil component that improves the DC bias characteristics. As shown in FIG. 14, the layered coil component 101 has a structure in which a nonmagnetic layer 104 is disposed between magnetic layers 102. Since the nonmagnetic layer 104 is disposed between the magnetic layers 102, the magnetic resistance of the magnetic paths φ′1 formed around a coil L is increased in the nonmagnetic layer 104, and a magnetic flux leaks from the nonmagnetic layer 104. As a result, the magnetic flux density is prevented from becoming excessively increased in the nonmagnetic layer 104, so that magnetic saturation becomes resistant to occurrence and sharp reduction in the inductance due to the magnetic saturation is suppressed. That is, the DC bias characteristics of the layered coil component 101 are improved.
However, with respect to the layered coil component 101 shown in FIG. 14, the DC bias characteristics cannot be improved satisfactorily. The reason will be described below.
As described above, the magnetic resistance of the magnetic path φ′1 is increased in the nonmagnetic layer 104. When the magnetic resistance is increased, as shown in FIG. 14, short magnetic paths φ′2 are generated so as to avoid the nonmagnetic layer 104. Since the magnetic paths φ′2 are closed magnetic circuits, a leakage of magnetic flux on the magnetic paths φ′2 is made difficult. Consequently, even when the DC bias current is relatively small, the magnetic density becomes excessively increased and the magnetic saturation may occur.